Dynamic Global Vegetation Models (DGVM) are powerful tools for studying complicated ecosystem processes and global changes. This review article synthesizes the developments and applications of the Integrated Biosphere Simulator (IBIS), a DGVM, over the past two decades. IBIS has been used to evaluate carbon, nitrogen, and water cycling in terrestrial ecosystems, vegetation changes, land-atmosphere interactions, land-aquatic system integration, and climate change impacts. Here we summarize model development work since IBIS v2.5, covering hydrology (evapotranspiration, groundwater, lateral routing), vegetation dynamics (plant functional type, land cover change), plant physiology (phenology, photosynthesis, carbon allocation, growth), biogeochemistry (soil carbon and nitrogen processes, greenhouse gas emissions), impacts of natural disturbances (drought, insect damage, fire) and human induced land use changes, and computational improvements. We also summarize IBIS model applications around the world in evaluating ecosystem productivity, carbon and water budgets, water use efficiency, natural disturbance effects, and impacts of climate change and land use change on the carbon cycle. Based on this review, visions of future cross-scale, cross-landscape and cross-system model development and applications are discussed.

The National Forest Inventory (NFI) is an important resource for estimating the national carbon balance (These data were unpublished data, and we could only obtain the data before 2008 through data search by now). Based on the data from sample plots, the literature, and NFI, as well as the relationships between volume, biomass, annual litterfall and soil respiration of different forest types, the net ecosystem production (NEP), changes in forest biomass carbon storage (ΔCbiomass) and non-respiratory losses (NR) of China's forests during 1999–2008 were estimated, and the forest soil carbon sequestration (ΔCsoil) was assessed according to the carbon balance principle of the forest ecosystem (ΔCsoil = NEP – NR – ΔCbiomass). The results showed that the total NEP, ΔCbiomass, NR and ΔCsoil values for China's forests were 157.530, 48.704, 31.033 and 77.793 Tg C yr^–1 respectively, and average NEP, ΔCbiomass, NR, and ΔCsoil values were 101.247, 31.303, 19.945 and 49.999 g C m^–2 yr^–1 respectively. There were large spatial differences in forest soil carbon sequestration in different parts of China. The forest soil in Jiangxi, Hunan, Zhejiang, Fujian, Anhui, Shanxi, Shaanxi, Guangxi and Liaoning served as carbon sources and the carbon released was about 25.507 Tg C yr^–1. The other 22 provinces served as carbon sinks and the average carbon sequestration by forest soil came to 103.300 Tg C yr^–1. This research established a method for evaluating soil carbon sequestration by China's forests based on the NFI, which is a useful supplement to current statistical data-based studies on the forest ecosystem carbon cycle, and can promote comparable studies on forest soil carbon sequestration with consistent research methods at the regional scale.

Vegetation restoration is the primary task of ecological reconstruction and rocky desertification control in Karst areas. With vegetation net primary productivity and coverage as two key indicators, a vegetation ecological quality evaluation model was built based on meteorological and remote sensing data. Spatiotemporal variation of vegetation ecological quality index and its response to climate change in rocky desertification areas in Southwest China during 2000–2020 were also analyzed by using the difference method and linear trend method. The results showed that: (1) Vegetation ecological quality in rocky desertification areas in Southwest China showed a fluctuating upward trend during 2000–2020. In 2020, the vegetation ecological quality index reached 69.7, which was 19.9% and 9.3% higher than the averaged values for 2000 and 2000–2019, respectively, ranking the fourth highest since 2000. (2) Vegetation ecological quality of the rocky desertification areas in Yunnan, Guangxi and Guizhou provinces have been improved by 89.2%, 99.2% and 98.5%, respectively, from 2000 to 2020, with their vegetation ecological quality index values increasing by 0.5–0.75 per year in southeast Yunnan, most areas in Guizhou and northwest Guangxi. (3) Precipitation was an important meteorological factor affecting the vegetation ecological quality in rocky desertification areas. The vegetation ecological quality index in the northwest and central Yunnan rocky desertification areas has been rising slowly, but with localized declines at a yearly rate of nearly 0.25 caused by climatic warming and drying.

Leaf longevity is an important adaptive strategy that allows plants to maximize photosynthetic carbon gain. Due to the difficulty of identifying overwintering bud scars and distinguishing the age sequence of twigs, leaf longevity is rarely studied in Cupressaceae species, which further limits our understanding of the leaf economic spectrum (LES) for these populations. Here, we investigated the leaf longevity, as well as mass-based leaf nitrogen concentration (N_mass), of Juniperus saltuaria at different canopy heights for both subalpine and alpine timberline forests in the Sergymla Mountains, southeastern Tibet. We found that the mean leaf longevity was 4.2±1.2 years, and overall it did not differ significantly between different elevations. Along the vertical profiles of juniper canopies, the leaf longevity did not reflect a linear trend. With increasing leaf longevity, N_mass showed declining trends. We further analyzed the relationship between leaf longevity and the corresponding length of green twigs, and found that the length of green twigs could only explain 1%–3% of the variation in leaf longevity, indicating that the length of green twigs is a poor predictor for the variation in leaf longevity. In summary, for the J. saltuaria species in timberline or nearby subalpine forests, the effects of elevation and canopy depths on leaf longevity are minor, and the leaf trait analysis is in accordance with the prediction of LES.

The reintroduction of rare and endangered species is one of the most important approaches to conservation and ecosystem restoration, but it has still proven to be an adventurous undertaking and most reintroduction programmes fail, so successful demonstrations are needed. Père David's deer (Elaphurus davidianus, Milu in Chinese) could be considered one of conservation's great success stories, as this species' path on the road to extinction has been reversed by a combination of ex-situ conservation and successful re-introduction in China. The species had been consigned to an imperial hunting ground when the last Chinese herds were exterminated during the fall of the Qing Dynasty (1644–1912). Fortunately, a few of the last remaining individuals were sent to European zoos. From these animals, a herd was bred on the 14^th Duke of Bedford's estate, Woburn Abbey, and between 1985 and 1987, and 38 Milu were donated back to China for re-introduction in Beijing Milu Park (BMP), the former imperial hunting ground. An additional 39 deer were released at Dafeng National Nature Reserve (DFNNR), Jiangsu Province in 1986. In both of these safe and protected locations, the Milu thrived allowing for over 700 Milu to be sent to a further 82 sites throughout the species' original Chinese range over the last 36 years. As a result, the Milu population totaled 9136 by 2021, with 2855 individuals now living back in the wild; while another 5681 individuals inhabit the DFNNR, and 186 reside in BMP. Wild Milu, however, still face significant conservation challenges. The population lacks genetic diversity, leading to severe inbreeding depression and carrying multiple risks, such as high miscarriage rates, a reduced lifespan, and susceptibility to disease. Environmental constraints such as pollution and habitat fragmentation further result in small, fragmented wild populations. Moreover, the species currently lacks a national level conservation master plan, the associated coordinated monitoring platforms, and breeding plans for China's captive populations. Finally, there is now a lack of international cooperation in the conservation of this species. We therefore call for both a national-level conservation master plan in China and international cooperation to develop a shared database and germplasm databank covering Milu across all countries with ex-situ populations, as crucial steps for securing the long-term conservation of Milu and preventing it from ever becoming “extinct in the wild” again.

As a new type of heritage, Agricultural Heritage Systems (AHS), represented by Globally Important Agricultural Heritage Systems (GIAHS) designated by Food and Agriculture Organization of the United Nations (FAO) and Nationally Important Agricultural Heritage Systems (NIAHS) designated by some countries' Ministry of Agriculture, are typical Social-Ecological Systems (SES), which usually are rich in biodiversity, traditional knowledge, resource utilization technology and outstanding cultural landscapes. Cultural Keystone Species (CKS) are defined as the culturally salient species that shape the cultural identity of a people in a major way. CKS can be used as a prominent tool for the synergistic conservation of SES biology and culture, and to promote the overall enhancement of system functions. This paper summarizes a review of the definition of the CKS and its application in SES conservation. According to the characteristics and protection needs of AHS, this paper defined the CKS in AHS as: “Composites of biological resources and cultural practices, which have a significant impact on the stability of local society and culture systems, contribute to the achievement of AHS' conservation goals.” Based on this definition, we analyzed the significance of the identification of CKS in AHS. First of all, CKS help to quickly identify the key elements of AHS. Secondly, CKS can promote community participation in the conservation and development of AHS. In addition, the identification of CKS has a significant role in food and livelihood security, biodiversity conservation, traditional knowledge and technology transmission, social organization maintenance, and cultural landscape maintenance in AHS, which helps to achieve the conservation goals of GIAHS and/or NIAHS.

Invasive species and habitat degradation are the main reasons for freshwater biodiversity loss. Reports on the habitat degradation and invasion ecology of Red Swamp crayfish (Procambarus clarkii) are few, although it is one of the most devastating invasive species in freshwater ecosystems. Based on a three-year investigation during 2017–2019 in West Dongting Lake, this study used Principal Component Analysis (PCA), Generalized Linear Model (GLM) and Bayesian model to analyze the relationships of P. clarkii stocks and environment factors in natural and modified wetlands. The results showed that the abundance of P. clarkii was positively correlated with total nitrogen, total phosphorus, water temperature, pH, water depth, and water transparency; while it was negatively correlated with dissolved oxygen and redox potential. The difference between P. clarkii stocks in natural and modified wetlands was nonsignificant. The P. clarkii stock decreased yearly, as levels in both 2018 and 2019 were significantly lower than in 2017. We concluded that inter-annual variation of the hydrological regime plays an important role in P. clarkii dynamics, and thus it is of great importance to ensure that the water level and flow velocity in summer to control the invasive P. clarkii.

Ecosystem services have rapidly changed at the global and regional scales in recent years. Exploring the driving mechanisms of ecosystem services change and projecting future change are of increasing importance to inform policy and decision-making options for ecosystem conservation and sustainable use. Although some research has analyzed the influences of land use or climate changes on ecosystem services, a systematic review on the mechanisms of ecosystem services change has not been carried out so far. This work elaborated on the mechanisms of ecosystem services change based on a literature review, and reached four main conclusions. (1) Climate change and land use jointly determine the ecosystem services change through complex and interacting pathways. (2) Whereas the present research progresses mainly focus on the identification of a single influencing factor, they fail in the determination of multiple influencing factors. (3) Although multi-scenario simulations based on remote sensing and climate models are the main means used to predict future changes in ecosystem services, clarifying the interactive mechanisms of multiple factors is the precondition for future projection of ecosystem services change; (4) Therefore, future research should strengthen the analysis and simulation of the effects of human activities on ecosystem services, especially the development of technology to detect the dynamic responses of ecosystem services to major ecological projects, which is crucial to the selection of restoration measures and the regional arrangement of ecosystem conservation projects.

Ecological compensation is an important part of ecological civilization which has gained widespread attention in academia in recent years. This study uses the knowledge graph tool CiteSpace to identify and analyze the literature related to ecological compensation research published in academic journals in the CNKI database, in order to provide an objective and scientific reference for the research in this field. The results show that the domestic research on ecological compensation began to appear around 2000, and the first research boom was ushered in starting in 2009. Most studies have explored ecological compensation from the connotation of ecological compensation, compensation subjects and objects, compensation standards, compensation methods, compensation supervision and evaluation of compensation effects, etc., and the articles on ecological compensation standards are relatively more abundant. At the same time, ecological compensation research is often linked to the realization of ecosystem service value and ecological product value. In the future, researchers should focus on establishing and improving the ecological compensation standard accounting system, exploring the market-based ecological compensation mechanism, attaching importance to the ecological compensation fund distribution mechanism, and strengthening research related to ecological compensation effect assessment. Ecological compensation theory should be developed in the direction of deepening and providing new research perspectives for helping China to deal with the relationship between conservation and development.

Agricultural production is considered one of the most important sources of water quality deterioration in the Taihu Lake Basin, China. Crop farming, livestock & poultry breeding and aquaculture are primary agricultural non-point sources and their impacts on the water environment are, in most cases, evaluated separately. Therefore, it is a challenge for current research to consider all of the different agricultural non-point sources as a whole and assess their combined influence on the water environment. The purpose of this paper is to evaluate the conjoint impact that agricultural non-point sources such as crop farming, livestock & poultry breeding and aquaculture have had on the local water environment in the Taihu Lake Basin by taking Huzhou City of Zhejiang Province as a case study. To achieve this, a new, innovative approach named the “Waste Absorption Footprint” (WAF) is applied. The results show that nitrogen and phosphorus pollution generated by agricultural production are more serious than that of organic substances, while aquaculture and crop farming are more critical pollution sources compared with livestock and poultry breeding, and so they should be the focus of environmental management and pollution control initiatives. There is a regional discrepancy in the spatial distribution of agricultural non-point source pollution across counties and districts, which provides information for determining the key regions for the treatment of agricultural pollution. This study demonstrates that the WAF method can make a comprehensive assessment of the influence of agricultural production on the water environment and provide references for the control and management of agricultural non-point source pollution, which is of great importance for management of the water environment.

Forests are the main components of terrestrial ecosystems and play an important role in the protection and construction of the national ecological security barrier. For a long time, China's large-scale afforestation had been practiced in areas with rainfall higher than the 400 mm threshold, but the issue of afforestation in high altitudes on the Tibetan Plateau remains elusive in both practical experience and theoretical exploration. It is worth thinking further about what principles should be followed in the selection of tree species and suitable altitudes for afforestation in high-altitude areas, as well as what experiences and lessons of previous afforestation efforts should be applied in high-altitude areas. As per the law of vegetation zonal distribution, this paper argues that afforestation at high altitudes should comply with the principle of vegetation zonal distribution and the low temperature limitation, and points out that afforestation is feasible only within the forest distribution area and below the altitudes of climate timberlines. Furthermore, we demonstrate the potential spatial areas of afforestation, and determine the local tree species that may be used for afforestation based on the existing problems of afforestation in eastern Tibet. In summary, afforestation in high-altitude areas of the eastern Tibetan Plateau must comply with the law of zonal vegetation distribution, focus on the upper limit of altitude and the selection of suitable tree species, and adopt only suitable native tree species.

The cushion plant Androsace tapete is an endemic species that is widely distributed in the Qinghai-Tibetan Plateau, and also predominant in the alpine grassland that is locally degraded due to overgrazing and other reasons. As an ecosystem engineer cushion plant, its ability to facilitate the restoration of degraded alpine grassland was studied in a degraded alpine grassland at an elevation of 4500 m on the southern slope of the Nyainqentanglha Mountains in Damxung. The species diversity, soil nutrients and water content underneath and outside the cushion plant A. tapete were investigated. The results showed that soil nutrients underneath the A. tapete cushion were significantly increased by about 16%–48% compared to outside the cushion, of which the organic matter and total N were increased by 16.2% and 18.9% respectively, and the soil water content was increased about 12%. The index of species diversity of richness (S), Shannon-Wiener's H and Simpson's D all increased with the coverage of cushion plant A. tapete. Our results suggested that this cushion plant can facilitate restoration of the degraded alpine grassland by modifying the local soil environment and increasing the community diversity, so it should be conserved for the restoration of degraded alpine grasslands on the Qinghai-Tibetan Plateau.

In order to construct stable vegetation for reducing wind and sand disasters and soil erosion in the Bashang Area of Northwest Hebei Province in China, it is very important to understand the ecological water demand of different vegetation types in this area. Based on observed data and the Irmak-Allen formula, we investigated the ecological water demand and ecological water shortage of arbor, shrub and grassland in Bashang Area of northwestern Hebei province. The results showed that the actual evapotranspiration values of the three vegetation types in the growing seasons in the study area from high to low were arbor forest (401.81 mm), shrub (358.78 mm) and grassland (346.02 mm). The minimum ecological water requirements of arbor forest, shrub and grassland in the growing season were 243.96 mm, 218.35 mm and 211.36 mm, respectively, and the optimal ecological water requirements were 472.99 mm, 423.34 mm and 409.77 mm, respectively. In addition, the optimal ecological water shortage values were 198.56 mm for arbor forest, 148.91 mm for shrub and 135.34 mm for grassland. The ecological water shortage of vegetation has obvious seasonality, with the largest water shortage in May and June, and a lower and steady water surplus in July to October. Therefore, an artificial water supplementation in May and June would alleviate the drought stress of the vegetation. The rainfall in Bashang Area of Northwest Hebei Province can meet the requirements of minimum ecological water demand for arbor forest, but the gap between the rainfall and the optimal ecological water requirement is too large to support good growth of an arbor forest, which could explain why the degradation of poplar protective forests has occurred in Bashang Area.

The Conversion of Farmland to Forests and Grasses Project is the most symbolic and globally important ecological engineering effort to build the human and natural life community. After the call and mobilization stage since the founding of the People's Republic of China, the first round of Conversion of Farmland to Forests and Grasses occurred at the end of the 20th century. With the second round of Conversion of Farmland to Forests And Grasses launched in 2014, the central government has invested 535.3 billion yuan altogether by 2020, and 34.83 million ha have been returned to forest and grassland in 25 provinces (autonomous regions and municipalities) (2435 counties included). Among them, 14.23 million ha were returned from farmland; barren hills and wasteland afforestation accounted for 17.53 million ha; and sealed mountain forest cultivation represented 3.07 million ha, accounting for 40% of the total afforestation area of national key projects in the same period, and 41 million households and 158 million farmers benefited directly. The project construction has made great achievements. The total value of ecological benefits has reached 1.42 trillion yuan, plus economic benefits of 0.26 trillion yuan, and social benefits of 0.73 trillion yuan, for a total amount of 2.41 trillion yuan. This effort has made outstanding contributions toward building an ecological civilization and a beautiful China. Looking forward to the future, the Conversion of Farmland to Forests and Grasses will embark on a new stage of high-quality development, which will strive to achieve high-quality construction, high efficiency and a high level of management. China will promote the third round of conversion of farmland to forest and grassland from 2021 to 2035, and it is expected to return 6.67 million ha to forests and grasses.

The accurate simulation and prediction of grassland aboveground biomass (AGB) and theoretical livestock carrying capacity are key steps for maintaining ecosystem balance and sustainable grassland management. The AGB in fenced grassland is not affected by grazing and its variability is only driven by climate change, which can be regarded as the grassland potential AGB (AGB_p). In this study, we compiled the data for 345 AGB field observations in fenced grasslands and their corresponding climate data, soil data, and topographical data on the Qinghai-Tibetan Plateau (TP). We further simulated and predicted grassland AGB_p and theoretical livestock carrying capacity under the climate conditions of the past (2000–2018) and future two decades (2021–2040) based on a random forest (RF) algorithm. The results showed that simulated AGB_p matched well with observed values in the field (R² = 0.76, P < 0.001) in the past two decades. The average grassland AGB_p on the Tibetan Plateau was 102.4 g m^–2, and the inter-annual changes in AGB_p during this period showed a non-significant increasing trend. AGB_p fluctuation was positively correlated with growing season precipitation (R² = 0.57, P < 0.001), and negatively correlated with the growing season diurnal temperature range (R² = 0.51, P < 0.001). The average theoretical livestock carrying capacity was 0.94 standardized sheep units (SSU) ha^–1 on the TP, in which about 54.1% of the areas showed an increasing trend during the past two decades. Compared with the past two decades, the theoretical livestock carrying capacity showed a decreasing trend in the future, which was mainly distributed in the central and northern TP. This study suggested that targeted planning and management should be carried out to alleviate the forage-livestock contradiction in grazing systems on the Tibetan Plateau.

With the development of tourism, the number of tourists and the scope of tourism activities are increasing, and the impact of tourism on the ecological environment is gradually revealed. The ecological environment is the foundation of sustainable tourism development. Some tourist destinations lack systematic and scientific evaluation and the proper planning of tourism resources, which makes it difficult for local areas to cope with the influx of a large number of people. In these destinations, the internal system is perturbed by a series of disturbances, which leads to bad effects on the local ecological environment. In addition to endangering the development of tourism, the quality of life of local residents is also threatened. Consequently, the issues between tourism and environment have become a hot topic in the field of tourism research. Through the collection of domestic and foreign tourism literature related to ecological theories since 1990 to 2020, the status of the application of various ecological theories in the field of tourism is revealed, such as life cycle theory, landscape ecology theory, carrying capacity theory, biodiversity, ecological niche theory and ecological footprint theory. This analysis found that the application of these theories to tourism mainly focuses on empirical research, and there are few studies on the basic theories related to it. In the empirical research, innovation of the research methods is basically absent. Therefore, future research should pay more attention to the theoretical research of ecological theory in the field of tourism, and combine modern science and technology in the practical application to strengthen the innovation of research methods. In addition, the prospect of applying ecological theories in future tourism research is discussed.

Green development is an important way to achieve global sustainable development goals, and has become one of the main research hotspots in recent years. Balancing economic development and environmental protection has turned out to be a great challenge in Beijing, the capital of China, which can provide some suggestions on ecological civilization construction and green development for other cities. However, there have been limited studies on this crucial topic. Therefore, based on the statistical data for Beijing from 2006 to 2016, this paper constructed the green development evaluation system of Beijing, and used the Projection Pursuit Model and spatial analysis method to analyze the spatial and temporal changes in its green development level. We also aimed to further explore the influences of key factors on green development. Our results illustrated that: (1) the overall and average levels of green development in Beijing showed significant increasing trends; (2) there are obvious spatial differences in green development among districts in Beijing, with the outer districts showing higher values; and (3) the environmental condition and human consumption were two important factors driving the green development in Beijing.